1. Field of the Invention
This invention relates generally to transparencies, such as but not limited to transparencies for furnaces, conventional ovens, microwave ovens, convection-microwave ovens, self-cleaning ovens, refrigerators, fireplaces, and the like. In one particular aspect, this invention relates to a coated panel for use in an appliance transparency and to appliance transparencies incorporating at least one such coated panel.
2. Description of the Currently Available Technology
Appliances, such as furnaces, conventional ovens, microwave ovens, convection-microwave ovens, self-cleaning ovens, and refrigerators, just to name a few, often have a transparency through which material inside the appliance can be viewed. These appliance transparencies also typically have heat or radiation reflecting elements to reduce heat or radiation passing through the transparency.
For example, conventional oven doors typically have a transparency formed by three or four spaced glass sheets. The glass sheets are typically about 5 mm thick. The two inner sheets (closest to the oven interior) have heat reflective coatings on both their inner and outer surfaces to reduce heat from the interior of the oven escaping into the ambient atmosphere. For example, it is known to provide a conventional oven door transparency in which the inner and outer surfaces (the No. 1 and No. 2 surfaces) of the innermost sheet and also the inner and outer surfaces (the No. 3 and No. 4 surfaces) of the adjacent sheet are coated with a heat reflective fluorine-doped tin oxide coating. Conventionally, for ovens the No. 1 surface is defined as the innermost surface (i.e., the surface closest to the heat source) and the other surfaces are numbered consecutively by counting outwardly from the No. 1 surface. This fluorine-doped tin oxide coating is typically applied to the glass sheets by spray pyrolysis. While adequate for heat reflection, this conventional appliance transparency structure does have some drawbacks. For example, spray pyrolysis of the fluorine-doped tin oxide coatings can result in uneven coating thickness across the surface of the sheet. This uneven coating thickness can lead to color and reflectance variations in the coated sheet that can be aesthetically undesirable. Additionally, this conventional oven transparency structure requires the application of four separate coatings (one coating on each side of the inner two sheets).
Conventional “self-cleaning oven” doors are similar to conventional oven doors but must meet certain industry recognized safety standards, such as a maximum permissible outer temperature during cleaning, in order to be sold in the United States. In order to meet these standards, conventional self-cleaning oven doors typically have a vent system to allow for convective flow of ambient air through the door to help carry away heat to decrease the temperature of the outer door during the cleaning cycle. However, this convective flow of ambient air introduces heated air into the kitchen and can increase the ambient temperature in the kitchen, making the kitchen uncomfortable to work in.
Conventional microwave oven doors are typically formed by an inner polymeric panel (such as a Mylar® sheet), an intermediate wire mesh grid, and an outer glass sheet. The inner Mylar® panel provides ease of cleaning and the intermediate wire mesh grid prevents microwave radiation from the interior of the oven passing through the transparency. Again, while adequate for its intended purposes, this conventional microwave oven door structure does have some drawbacks. For example, the conventional microwave oven door requires three separate pieces that must be assembled in order for the door to function properly. Moreover, it may be difficult to adequately view material inside the oven through the wire mesh grid.
Therefore, it would be advantageous to provide a coated sheet or panel that can be utilized in appliance transparencies that reduces or eliminates at least some of the drawbacks described above. For example, it would be advantageous to provide a conventional oven door in which fewer than four coatings were needed to provide acceptable performance. It would be advantageous to provide an oven door, such as a self-cleaning oven door, in which the conventional vent system can be reduced or eliminated while still meeting the recognized safety standards. Additionally, it would be advantageous to provide a microwave oven transparency that eliminates at least some of the required components of conventional microwave oven transparencies and/or provides increased visibility through the microwave oven transparency.